A sudden infection of the tissues immediately surrounding the eye, resulting in painful swelling of the upper and lower eyelid, and possibly the eyebrow and cheek. Other symptoms include bulging eyes, decreased vision, fever, and eye pain when moving the eyes. Bacteria from a sinus infection are a common cause; other causes include a stye on the eyelid, bug bites or a recent eyelid injury. Orbital cellulitis is a medical emergency and prompt IV antibiotic treatment often is needed to prevent optic nerve damage, permanent vision loss or blindness and other serious complications.